[Two cases of gastrointestinal stromal tumor (GIST) of the stomach and a consideration of its malignancy potential and treatment strategy - report of two cases].

We report two cases of large gastrointestinal stromal tumor (GIST) of the stomach both of which were assessed as highly malignant, but took different clinical courses. Case 1: A 72-year-old male. Case 2: A 63-year-old female. The tumor size of Case 1 was suggestive of high malignancy, but only a partial gastrectomy was selected because it did not show any invasive findings. This patient has been followed up for 3 years post-operatively and no recurrence or metastasis has been noted. Case 2 had liver and lymph node metastases, which was consistent with high malignancy. We performed a total gastrectomy with distal pancreatosplenectomy and segmental liver resection. But after surgery, liver metastasis recurred therefore, imatinib mesylate was administered as adjuvant chemotherapy and since then, the tumor has been diminishing in size. No definitive evidence for adjuvant therapy has been established so far, but we suggest that post-operative adjuvant therapy is effective for high-risk GIST.